DE69736578T2 - SURFACE LIGHT SOURCE, LIQUID CRYSTAL DISPLAY DEVICE AND ASYMMETRIC PRISM PLATE - Google Patents

Description

FIELD OF THE INVENTION

The Invention relates to a surface light source device, in the one light scattering guide plate (a plate-like light scattering guide), a liquid crystal display, the light scattering guide plate for the Lighting used from the back, and an asymmetrical prism board used for that can use advantageous. In this patent the designated Term "asymmetric Prism board "a" board-like optical Element that has a prism surface contains through numerous lines of asymmetric prism elements is formed ".

BACKGROUND OF THE INVENTION

Light source devices, in which a light scattering guide plate and a prism board are used and are proposed for different Purpose used, for example, for the backlighting of liquid crystal displays. A conventional one Prism board consists of a plate-like part, which consists of a made of optical material having a prism surface, the repetitive lines of v-shaped irregularities is trained. As is known, such a prism board has the function of to change the direction propagation characteristics of a beam.

1 Fig. 10 shows a general arrangement of a conventional surface light source apparatus in which a light diffusing guide plate and a prism sheet are used. A light scattering guide plate 1 , which has a wedge-shaped portion, consists of a matrix made of polymethylmethacrylate (PMMA) and of a material of a different refractive index which is mixed and uniformly dispersed in the matrix. The term "material with a different refractive index" refers to a material that has a refractive index that differs considerably from the refractive index of the matrix.

One of the end faces, which is the end face of the light scattering guide plate 1 with the larger thickness, serves as the incident surface 2 , In the vicinity of the incident surface, a light source device (fluorescent lamp) L is disposed.

A reflector 3 is along a surface (the back surface 6 ) of the light scattering guide plate 1 arranged. The reflector 3 consists of a sheet of silver foil with regular reflectivity or a white sheet with diffuse reflection. Illumination light is obtained at an exit surface 5 on the opposite side of the light scattering guide plate 1 , The prism board 4 is outside the exit area 5 arranged.

For better visibility in the drawing, the interval between the light scattering guide plate 1 and the lines of the prism elements and the distance and the depth of the lines of the prism elements exaggerated. The inner surface of the prism board 4 is a prismatic surface caused by repeated symmetrical v-shaped flanks 4a and 4b is formed. The outer surface of the prism board 4 forms a flat surface (luminous surface) 4e from which an illuminating ray 4f exit. A backlight assembly for a liquid crystal display can be constructed by placing a known liquid crystal display panel outside the prism panel 4 arranges.

The thickness of the light scattering guide plate 1 increases with increasing distance from the incident surface 2 from. This is done within the light scattering guide plate 1 effectively repeated reflection. As a result, the surface light source device has excellent light utilization and uniform luminous intensity.

That of the light source device L in the light scattering guide plate 1 registered light becomes an end face 7 guided, which determines the smaller thickness of the plate, and in the light scattering guide plate 1 scattered and reflected. In the course of this process, the illuminating light gradually from the exit surface 5 sent out.

That from the exit surface 5 emitted light has a preferred propagation direction, which depends on the particle diameter of the particles with the other refractive index, in the light scattering guide plate 1 distributed (in general terms, the correlation distance associated with the nonuniform refractive index structure). D. h., The exit surface 5 emits a beam that is more or less collimated.

The larger the diameter of the particles having a different refractive index (in general, the larger the correlation distance associated with the non-uniform refractive index structure), the greater the exit surface area 5 emitted light collimates. The preferred direction of propagation (the main direction of propagation of the illuminating rays) is normally a direction which defines upwardly an angle of approximately 25 ° to 30 ° with the exit surface, as viewed from the incident surface 2 ,

In this way, the prism board works 4 when changing the direction propagation characteristics.

2 shows a view showing the behavior of the light in a section in the longitudinal direction of the arrangement in 1 explained. The term "longitudinal direction" refers to a direction parallel to the direction in which the light of the light scattering guide plate 1 is supplied (ie, perpendicular to the incident surface 2 ). In contrast, a direction which is perpendicular to the direction in which the light of the light scattering guide plate becomes 1 (ie, parallel to the incident surface 2 ) is referred to as "transverse direction".

In 2 is the prism board 4 along the exit surface 5 the light scattering guide plate 1 arranged, with the prism side pointing inwards. A preferred angle φ3 for the apex angle of each of the prism elements forming the line of prism elements is about 60 °.

If the direction of incidence is indicated by the arrow L ', then the preferred propagation direction of the beam, that of the exit surface, determines 5 is emitted, an angle φ2 = about 60 ° to the normal to the exit surface 5 ,

Assuming that PMMA (one of the usual matrix materials having a refractive index of n = 1.492) is used as the matrix of the light scattering guide plate 1 is used, it is achieved with an angle of incidence of φ1 = about 35 ° on the exit surface 5 an angle φ2 = about 60 °.

One Beam leading to such a preferred propagation direction belongs, is called a "representative beam". In this Case is the most representative Beam marked with the reference B1.

The representative beam B1, the exit surface 5 emits a straight line through a layer AR of air (which has a refractive index n0 = about 1.0) and then hits an edge 4a the prism board 4 at an angle close to the right angle (φ3 = about 60 °). The percentage of rays on another flank 4b fall, is relatively low.

Thereafter, the representative beam B1 moves substantially rectilinearly in the prism sheet 4 to the opposite flank 4b and is reflected there regularly.

The beam subjected to regular reflection strikes the plane surface 4e the prism board 4 at an angle close to the right angle, and leaves the prism table 4 out. This process alters the preferred direction of propagation of the beam, the exit surface 5 emits, in a direction substantially perpendicular to the exit surface 5 is.

However, one can choose the preferred propagation direction after the change against the direction perpendicular to the exit surface 5 move. The angle of displacement against the vertical direction can, to a certain extent, be dependent on the point angle φ3 of the prism table 4 , the material (refractive index) of the prism board 4 and the material (refractive index) of the light scattering guide plate 1 to adjust.

3 shows a further arrangement of the prism board 4 and the behavior of light. In this arrangement, the prism surface faces outward. The apex angle φ4 of each prism element on the prism surface is about 70 °, for example.

at This arrangement is the range of point angles, the preferred Yields results wider than in the described arrangement, in the prism surface pointing inwards.

Assuming that the direction of incidence is the direction indicated by the arrow L ', a representative beam B2 corresponding to the preferred direction of propagation falls on the exit surface at an angle φ1 = about 35 ° 5 , The beam is mostly emitted into the layer AR of air (which has a refractive index n0 = 1.0). The exit angle φ2 is approximately 60 ° in this case.

The representative beam B2 moves in a straight line through the layer AR of air and then hits at an angle on the flat surface 4e the prism board 4 , The beam follows the illustrated reflection path and is from a surface 4c the prism board 4 at an angle near the right angle to the exit surface 5 sent out. The percentage of rays coming from the other surface 4d to be sent out is relatively modest.

The path of the beam after the incident on the flat surface 4e the prism board 4 depends on the refractive index n2 of the prism board 4 and the apex angle φ4 of the prism. It is therefore possible to adjust the preferred propagation direction by influencing these parameters.

The described conventional Surface light source device Fulfills However, not all requirements for height and equal distribution of Brightness of the illuminated area (the top of the prism board), if you look them with the naked eye and the impression of dimness that the lighting conveys.

Different formulated, the prior art can not provide a luminous surface, which is pleasant, does not sparkle and is sufficiently white. One A major problem is the so-called reflection projection (the appearance of light and dark areas caused by reflection arise). Such a reflection projection influences, for example the display quality a liquid crystal display disadvantageous.

It is believed that this is due to the following reason. The light scattering guide plate 1 in the arrangement in 1 From the point of view, it does not have such a high throwing power. This tendency increases for larger luminous surfaces, for which one chooses a weaker throwing power. As a result, a considerable amount of light from the reflector 3 reflected at the back of the light scattering guide plate 1 is arranged. This amount of light hits the viewer's eyes without being sufficiently scattered.

Used as a reflector 3 a sheet with regular reflective properties, such as a sheet of silver foil or aluminum foil, gives an optical impression which clearly corresponds to a surface with regular reflection. Such a visual impression is accompanied by the so-called "white defect" and the "lack of softness or glitter impression". Sometimes you can see wrinkles or grooves through the prism board.

you can assume that such phenomena and the impressions that they convey to the viewer, not only by the amount of light are determined by multifactorial effects such as the Color temperature and the directional propagation characteristics of the illuminating Beam.

The difficulty with the white component can be alleviated to some degree by using a white sheet with diffuse reflectivity as a reflector 3 used. However, this results in a reduced uniformity of the brightness and the amount of light of the luminous area as a whole. Regardless of whether the reflector used has regular or diffuse reflection properties, any nonuniformity (eg, local wrinkles or perturbations) on the surface of the reflector 3 cause visible nonuniformities.

• (1) Entlang der Rückseite der Lichtstreuungs-Führungsplatte wird eine eigene Prismentafel angeordnet. Diese Prismentafel ist so ausgerichtet, dass die Zeilen der Prismenelemente parallel zur Richtung verlaufen, in der das Licht zugeführt wird (japanische Patentschrift Nr. H7-74671).

The inventor gives the following two proposals for solving the problems described.

• (1) A separate prism sheet is placed along the back of the light-scattering guide plate. This prism sheet is aligned so that the lines of the prism elements are parallel to the direction in which the light is supplied (Japanese Patent Publication No. H7-74671).

• (2) Man verwendet eine doppelseitige Prismentafel als Prismentafel, die auf der Seite der Austrittsfläche der Lichtstreuungs-Führungsplatte angeordnet ist (japanische Patentschrift Nr. H7-213964, siehe auch JP-A-07-270708). Diese doppelseitige Prismentafel ist mit Zeilen aus Prismenelementen auf beiden Seiten ausgebildet, die senkrecht zueinander verlaufen.

This first proposal solves the problems described. However, two prism sheets are needed, and further improvements are needed to achieve a compact structure and lower manufacturing costs.

• (2) Use a double-sided prism sheet as a prism sheet disposed on the side of the exit surface of the light-scattering guide plate (Japanese Patent Publication No. H7-213964, see also JP-A-07-270708). This double-sided prism sheet is formed with lines of prismatic elements on both sides that are perpendicular to each other.

The Prism board is aligned so that the lines with the prism elements on the inner prism surface parallel to the incident surface run and that the lines with the prism elements on the outer prism surface perpendicular to the incidence area run.

Of the Point angle of the prisms on the inner prism surface is designed with an angle at which light differs from the light scattering guide plate propagates in the preferred propagation direction, substantially in a forward direction guided in the prism board becomes.

in the Contrast, the apex angle of the prisms is designed on the outer prism face so that's essentially in a forward direction in the prism board guided Light is shifted in one direction, which is essentially perpendicular to light supply direction runs, and subsequently inverted (thrown back) becomes. A common one Value for such a prism tip angle is 90 °, and the actual Area for this Angle is between about 70 ° and approximately 130 °.

This second suggestion improves the height and uniformity the brightness, suppressed Reflections and improves the appearance (proportion of white and softness) of the luminous surface and at the same time solves the problems that the first proposal described does not solve.

• (1) Weitere Verbesserung des Helligkeitspegels einer Anzeige, falls sie in einer Hauptbetrachtungsrichtung betrachtet wird (im Wesentlichen die Vorwärtsrichtung).
• (2) Es liegen Forderungen nach Merkmalen vor, beispielsweise dass der Helligkeitspegel mit einer zunehmenden Winkelabweichung von der Hauptbetrachtungsrichtung (im Wesentlichen der Vorwärtsrichtung) allmählich abnimmt, und dass die Ausgabe von Beleuchtungslicht in den Betrachtungsrichtungen soweit wie möglich unterdrückt wird, in der eine Betrachtung wenig wahrscheinlich ist, damit eine nutzlose Beleuchtung vermieden wird. Um eine solche Forderung zu erfüllen, muss man eine optische Ausgabe in Richtungen, die von der Vorwärtsrichtung um 30 Grad oder mehr abweichen, so weit wie möglich unterdrücken.

For the illumination light, which is used for example for the backlighting of liquid crystal displays, but increasingly higher qualities are required. These requirements include the recent needs that have arisen.

• (1) Further improvement of the brightness level of a display when viewed in a main viewing direction (substantially the forward direction).
• (2) Characteristics are required, for example, that the brightness level gradually decreases with increasing angular deviation from the main viewing direction (substantially the forward direction), and that the output of illumination light in the viewing directions is suppressed as much as possible, in the one viewing little is likely so that a useless lighting is avoided. In order to meet such a demand, it is necessary to suppress as much as possible an optical output in directions other than the forward direction by 30 degrees or more.

A surface light source device according to the described proposal is unsatisfactory in view of such requirements. In particular, this device does not have a performance feature similar to that described in (9) above. 2 ). This is apparent from an embodiment which will be described below for comparison purposes.

The Fact that unused lighting light is emitted in directions that is going strong from the forward direction differ, proving that there is still a need for improvement in point (1).

DISCLOSURE OF THE INVENTION

It It is a first object of the invention to provide a prism sheet for a surface light source device in which the brightness level is seen from the main viewing direction (essentially the forward direction) is improved.

It It is a second object of the invention to provide a prism sheet for a surface light source device in which the brightness level increases with increasing Angular deviation from the main viewing direction (essentially the forward direction) gradually drops and in which the output of unused illumination light in directions repressed which deviate greatly from the significant forward direction.

It a third object of the invention is to provide a prism board, the applicability of a surface light source device for liquid crystal displays improved.

According to the invention, a prism sheet is provided for use in altering the directional propagation characteristics of light emitting an exit surface of a light scattering guide plate having an incident surface which receives light, the prism sheet having a first surface on which rows of prism elements in a first Direction are aligned, and a second surface, are aligned with the rows of refractive elements in a second direction, which is perpendicular to the first direction,
wherein the rows of refracting elements on the second surface are provided with surfaces which cause a beam, which is guided in the prism sheet substantially in a forward direction, to be displaced in the first direction and then thrown back to the first surface,
characterized in that the rows of prism elements on the first surface are formed by alternating repetitions of an inclination having a first relatively small inclination angle with respect to the thickness direction of the prism sheet and an inclination having a second relatively large inclination angle with respect to the thickness direction, and the inclinations having the second inclination angle are directed toward the incident surface whereas the inclinations having the first inclination angle are directed away from the incident surface.

A Surface light source device, which is adapted to the invention comprises a light scattering guide plate, a primary one Light source device, which on the side of the light scattering guide plate is arranged and light to the incident surface of the light scattering guide plate sends a prism board along an exit surface of the Light scattering guide plate is arranged, and a reflector, which is arranged on the side is that of the exit surface opposite.

• (1) Die Prismentafel enthält Zeilen mit Prismenelementen auf einer ersten Oberfläche (Innenfläche) der Tafel und Zeilen mit Prismenelementen oder Linsenelementen auf einer zweiten Oberfläche (Außenfläche) der Tafel.

The prism sheet disposed along the exit surface is constructed and designed according to the following conditions (1) to (6).

• (1) The prism sheet includes lines having prismatic elements on a first surface (inner surface) of the panel and lines having prismatic elements or lens elements on a second surface (outer surface) of the panel.

• (2) Die Zeilen mit Prismenelementen auf der Innenfläche und die Zeilen mit Prismenelementen oder Linsenelementen auf der Außenfläche sind in zueinander senkrechten Richtungen (einer ersten und einer zweiten Richtung) angeordnet.
• (3) Die Prismentafel ist derart ausgerichtet, dass die Richtung, in der die Zeilen mit Prismenelementen auf der Innenfläche angeordnet sind (der ersten Richtung), parallel zur Einfallsfläche der Lichtstreuungs-Führungsplatte ist (senkrecht zur Richtung, in der Licht zugeführt wird). Unter dieser Bedingung für die Ausrichtung ist die Richtung, in der die Zeilen der Prismenelemente oder Linsenelemente auf der Außenfläche angeordnet sind (die zweite Richtung), offenkundig senkrecht zur Einfallsfläche der Lichtstreuungs-Führungsplatte (parallel zur Richtung, in der Licht zugeführt wird).
• (4) Die Zeilen der Prismenelemente oder Linsenelemente auf der Außenfläche sind so ausgebildet, dass Licht, das in der Prismentafel in Vorwärtsrichtung geführt wird, in eine Richtung verschoben wird, die im Wesentlichen senkrecht zur Richtung ist, in der das Licht zugeführt wird, und anschließend zur Innenfläche zurückgeworfen wird.
• (5) Ist die Außenfläche eine Prismenfläche, so haben die Zeilen der Prismenelemente bevorzugt einen Prismenspitzenwinkel im Bereich 70° bis 130°. Der besonders bevorzugte Wert für diesen Bereich liegt beispielsweise bei 96°.
• (6) Die Zeilen der Prismenelemente, die auf der inneren Prismenfläche ausgebildet sind, werden von sich wiederholenden Mustern mit einer Flanke gebildet, die einen relativ kleinen ersten Neigungswinkel hat, und einer Flanke, die einen zweiten relativ großen Neigungswinkel hat, wobei die Flanken abwechselnd angeordnet sind. Damit ist die Innenfläche eine Fläche, auf der eine Vielzahl von asymmetrischen Prismennuten ausgebildet und ausgerichtet sind.
• (7) Die Flanken mit dem zweiten Neigungswinkel der Zeilen der Prismenelemente, die auf der Innenfläche ausgebildet sind, sind hin zur Einfallsfläche gerichtet. Durch diese Bedingung sind die Flanken mit dem erstem Neigungswinkel offensichtlich entgegengesetzt zur Einfallsfläche gerichtet.
• (8) Der erste relativ kleine Neigungswinkel beträgt bevorzugt ungefähr 15°. Ein bevorzugter Wert für den zweiten relativ großen Neigungswinkel beträgt ungefähr 32,5 °.
• (9) Die Dicke der Lichtstreuungs-Führungsplatte nimmt bevorzugt mit wachsender Entfernung von der Einfallsfläche ab. In der Regel ist die Lichtstreuungs-Führungsplatte im Querschnitt keilförmig aufgebaut. Entlang einer der Stirnflächen, die die größere Dicke der Lichtstreuungs-Führungsplatte bestimmt, ist eine Lichtzuführanordnung untergebracht.

The inner surface is an area that receives illumination light from the light diffusion guide plate. The outer surface is an area from which the illumination light is emitted to the outside.

• (2) The lines having prism elements on the inner surface and the lines having prism elements or lens elements on the outer surface are arranged in mutually perpendicular directions (first and second directions).
• (3) The prism sheet is oriented such that the direction in which the rows of prism elements are arranged on the inner surface (the first direction) is parallel to the incidence surface of the light scattering guide plate (perpendicular to the direction in which light is supplied). Under this condition for alignment, the direction in which the lines of the prism elements or lens elements are arranged on the outer surface (the second direction) is apparently perpendicular to the incident surface of the light scattering guide plate (parallel to the direction in which light is supplied).
• (4) The lines of the prism elements or lens elements on the outer surface are formed so that light guided in the prism sheet in the forward direction is shifted in a direction substantially perpendicular to the direction in which the light is supplied, and then thrown back to the inner surface.
• (5) If the outer surface is a prism surface, then the lines of the prism elements preferably have a prism tip angle in the range 70 ° to 130 °. The most preferred value for this range is for example 96 °.
• (6) The lines of the prism elements formed on the inner prism surface are formed by repeating patterns having a flank having a relatively small first inclination angle and a flank having a second relatively large inclination angle, the flanks alternately are arranged. Thus, the inner surface is a surface on which a plurality of asymmetrical prism grooves are formed and aligned.
• (7) The flanks having the second inclination angle of the lines of the prism elements formed on the inner surface are directed toward the incident surface. By this condition, the flanks with the first inclination angle are obviously directed opposite to the incident surface.
• (8) The first relatively small inclination angle is preferably about 15 °. A preferred value for the second relatively large inclination angle is about 32.5 °.
• (9) The thickness of the light diffusing guide plate preferably decreases with increasing distance from the incident surface. In general, the light scattering guide plate is wedge-shaped in cross section. Along one of the end surfaces, which determines the greater thickness of the light scattering guide plate, a Lichtzuführanordnung is housed.

A Surface light source device, having the features set in the above items (1) to (9) are described, you can in a known arrangement way for backlighting a liquid crystal panel use. The use of such backlighting allowed not only the saving of electrical energy, but also provides about that In addition, a liquid crystal display ready with excellent viewing quality.

A prism sheet in accordance with the above-described conditions (1) to (8) can be regarded as a novel optical functional device having an asymmetric prism surface. in the As compared with the above-described double-sided prism sheet, which is a symmetrical prism sheet (see Japanese Patent Publication No. H7-213964), this asymmetrical prism sheet is characterized in that it effectively converts light incident on flanks with a relatively small inclination angle into light that spreads in the thickness direction.

The Invention also improves the properties of a surface light source device or a liquid crystal display according to the described second proposal (Japanese Patent Publication No. H7-213964). These Improvement of properties is based on the characteristics of asymmetric Prism board proposed by the invention.

Illumination light, that the exit surface the light scattering guide plate is emitted into the asymmetric prism board over the Flanks introduced, which have a relatively small tilt angle, and effective in light transformed, which spreads in the thickness direction of the prism board.

The light which has been subjected to the effective change in direction reaches the outer surface, is displaced in a direction perpendicular to the feeding direction of the light, and then thrown back toward the light scattering guide plate. The description in 3 it can be seen that a considerable portion of the light propagating in directions distributed around the preferential propagation direction of a representative beam undergoes a process of converging light propagating in the transverse direction (a direction perpendicular to the direction, in which the light is supplied), toward the forward direction, so that the brightness becomes stronger from the forward direction.

One certain percentage of the representative Beam, which is returned as described, is converted into light that is distributed around the representative beam is by going through different paths and finally by the outer surface of the Prism board is emitted.

These procedures allow the rays of light that are finally effective from the outer surface of the asymmetric Prism board are emitted, have different histories. This improves the visual impression they deliver and the reflection projection near the incident surface is suppressed.

SHORT DESCRIPTION THE DRAWINGS

It shows:

1 a view explaining an arrangement of a conventional surface light source device;

2 the behavior of light in a cross section along the longitudinal direction of the arrangement in 1 ;

3 a cross-sectional view illustrating the behavior of light in an arrangement in which the prism board in 1 or 2 is turned over;

4 a view explaining an embodiment of the invention;

5 (a) and 5 (b) Views for explaining the features of an asymmetric prism board of the invention, wherein 5 (a) represents the light propagation in a conventional symmetrical prism board and 5 (b) the light propagation in an asymmetric prism sheet of the invention;

6 Examples of the preferred inclination angles φa and φb of an asymmetric prism sheet of the invention and the effects of the angles;

7 the behavior of light near an outer prism surface of a prism sheet having a proper prism tip angle φ4;

8th the behavior of light near the outer prism surface of the prism sheet for too large a prism tip angle φ4;

9 the behavior of returned beams D1 and D2 near an inner prism surface che;

10 (a) a curve of the measurement results of the angle characteristics of illumination light in a longitudinal cross-section of a symmetrical prism board in the arrangement in 4 and under the conditions 6 , and 10 (b) a graph of the results of a similar measurement of the angular properties, which occur in a cross-section in the transverse direction under the same measurement conditions;

11 a curve of the angular properties measured in an arrangement which is designed exactly as the arrangement for the results in 10 (a) and 10 (b) but with the prism board removed;

12 a sketched partial view of a first alternative embodiment of the invention;

13 a sketched partial view of a second alternative embodiment of the invention;

14 a sketched partial view of a third alternative embodiment of the invention;

15 a sketched partial view of a fourth alternative embodiment of the invention;

16 a view illustrating a fifth alternative embodiment of the invention, in which a prism board is used, which has a prism surface and a lens field surface;

17 illustrates the operation of rows of lens elements formed on an outer surface of a prism sheet having a prism surface and a lens surface;

18 illustrates the configuration of lens elements of a prism sheet used in an assembly making up the in 19 (a) and 19 (b) obtained measurement results;

19 (a) a curve of the angular properties of illumination light in a cross section in the longitudinal direction of the arrangement 16 in the conditions in 6 , and 19 (b) a curve of the angular properties for a cross-section.

DESCRIPTION OF THE BEST ART TO PERFORM THE INVENTION

4 shows an arrangement of the essential parts of an embodiment of the invention. For better visibility in the drawing, the interval between a light scattering guide plate and the lines of the prism elements and the distance and the depth of the lines of the prism elements are exaggerated.

This embodiment is a structure obtained by using the prism sheet 4 in the conventional surface light source device in FIG 1 through a prism board 4 ' replaced the invention.

An end face that has the greater thickness of a light scattering guide plate 1 determined, which has a wedge-shaped cross section, serves as incident surface 2 , In the vicinity of the incident surface, a light source device (fluorescent lamp) L is disposed. The rear side of the light source device (fluorescent lamp) L is preferably surrounded by a reflector which consists of a sheet of silver foil or a similar part (not shown). Along the back surface 6 the light scattering guide plate 1 is a reflector 3 arranged. As a reflector 3 One uses a sheet of silver foil with regular reflectivity or a white sheet with diffuse reflection.

Illumination light is taken from an exit surface 5 the light scattering guide plate 1 , The asymmetric prism board 4 ' a type with double orthogonal prism surface is outside the exit surface 5 arranged. A liquid crystal display is formed by placing a known liquid crystal display panel LP (shown by the broken line) outside the prism sheet 4 ' arranges.

As with the surface light source device in FIG 1 takes the thickness of the light scattering guide plate 1 with increasing distance from the incidence surface 2 from. As described, this improves the efficiency of light utilization and the uniformity of lighting.

In the light scattering guide plate 1 introduced light becomes an end face 7 led, which determines the smaller thickness of the plate. At this time, the light in the light scattering guide plate becomes 1 scattered and reflected. During this process, illumination light is gradually emitted from the exit surface 5 emitted.

As already described possesses that of the exit surface 5 emitted light a preferred propagation direction, which depends on the particle diameter of the particles with the other refractive index, in the light scattering guide plate 1 distributed (in general terms, the correlation distance associated with the nonuniform refractive index structure). D. h., The exit surface 5 emits a collimated illumination beam.

The larger the diameter of the in the light scattering guide plate 1 distributed particles having a different refractive index (in general, the larger the correlation distance associated with the non-uniform refractive index structure), the sharper is the exit surface area 5 emitted light collimates. The preferred direction of propagation (the main direction of propagation of the illuminating rays) is normally a direction which defines upwardly an angle of approximately 25 ° to 30 ° with the exit surface, as viewed from the incident surface 2 ,

The light scattering guide plate 1 can be formed as in the conventional case of a material which is obtained, for example, by uniformly distributing a material with a different refractive index (eg silicone particles) in a matrix of polymethyl methacrylate (PMMA). The admixed percentage of the material with a different refractive index (in weight percent) is adjusted so that the light scattering guide plate 1 has a suitable throwing power.

In general, the larger the longitudinal dimension of the light scattering guide plate, the lower the percentage of the mixed material with a different refractive index 1 is. Is the throwing power of the light scattering guide plate 1 too large, it prevents the propagation of light in areas that are from the incident surface 2 are removed. This can lead to a brightness gradient on the luminous surface.

The particle size of the particles of different refractive index is one of the factors that determines the amount of forward tilt during each scattering operation in the light scattering guide plate 1 determine. In general, the larger the particles are, the greater the forward tendency. If the particles are relatively large, the preferred propagation direction of the jet is the exit surface 5 the light scattering guide plate 1 emits, clearly defines, and provides an illumination beam that resembles a collimated beam. If, on the other hand, the particles are relatively small, then the expressiveness of the preferred direction of propagation of the beam, that of the exit surface, goes 5 the light scattering guide plate 1 sent out, lost.

The particle size is preferably adjusted depending on the level of directivity required for the illumination beam. According to the invention, the composition of the material from which the light scattering guide plate is subject 1 is constructed, no special restrictions.

It will now be the structure and function of the prism board 4 ' described that has prismatic surfaces on both sides.

On the prism board 4 ' , please refer 4 , are flanks 4a and 4b as a unit repeated on the inner surface of the prism board 4 ' designed so that they form lines of prism elements. On the outer surface are flanks 4c and 4d as a unit repeatedly formed so as to form lines of prism elements thereon. As with the prism board 4 in 1 The rows of prism elements formed on the inner surface extend in a direction parallel to the incident surface 2 , In contrast, the lines of the prism elements formed on the outer surface are in a direction perpendicular to the incident surface 2 ,

It is important that the inclination angles φa and φb of the flanks 4a respectively. 4b are designed such that the relationship φa <φb is satisfied. In other words, a relationship φa = φb, which is valid for a symmetrical prism sheet, is not met in the asymmetric prism sheet of the invention.

Note that in the context of this patent specification, the angles of inclination of the flanks 4a and 4b of the respective prism element lines by means of the thickness direction N of the prism sheet 4 be defined as a reference (tilt angle of 0 °).

When installing the prism board 4 ' in the surface light source device, one selects the orientation of the flanks 4a such that a representative light beam, which corresponds to the preferred direction of propagation of directed light, that from the exit surface 5 leaking, essentially on the flanks 4a meets.

In detail, the flanks show 4a to the incidence area 2 , and the flanks 4b show away from the incidence area 2 , This causes light to be at an angle (a major component of the light that is the exit surface 5 sends out) on the flanks 4a meets, effectively in the forward direction in the prism board 4 ' guided.

5 (a) and 5 (b) show views that explain the reasons for this arrangement. 5 (a) shows how the rays S1 and S2, which meet at an angle to a symmetrical Prismentafel, are forwarded there. 5 (b) shows how rays S1 and S2, which are the rays in 5 (a) same, meet at an angle to an asymmetric prism board of the invention and be forwarded there.

The rays S1 and S2 show a sketch of the bandwidth of the propagation direction of the light, which is actually from the exit surface 5 is sent out and on a flank 4a meets. The diagonally incident beam S1 corresponds to a beam having a relatively small elevation angle (propagating in a direction farther from the forward direction), whereas the diagonally incident beam S2 corresponds to a beam having a relatively large elevation angle (extending in FIG a direction closer to the forward direction).

The flanks 4a and 4b , please refer 5 (a) , the symmetrical prism board have the same inclination angle φ0. The inclination angle φ0 is one half of the prism tip angle and is usually about 30 °. The beam S1 hits an edge 4a , then reaches another flank 4b and can be easily changed in its direction to the forward direction (total reflection).

In contrast, the beam S2 can not on the flank 4b hit because it is broken insufficiently (refraction in one direction that reduces the elevation angle) when it hits the flank 4a meets. So it is likely that it runs directly to the outer prism surface.

The inclination angles φa and φb of the flanks 4a and 4b , please refer 5 (b) in the asymmetric prism sheet of the invention satisfy the relationship φa <φb. The inclination angle φb corresponds to the inclination angle φ0 in 5 (a) , This can be φb in 5 (b) consider substantially equal to φ0; he usually has about 30 °. The beam S1 hits an edge 4a , then reaches another flank 4b and can be easily changed in its direction to the forward direction (total reflection). This corresponds completely to the case in 5 (a) ,

The beam S2 hits in relation to the beam in 5 (a) easier on the flank 4b because it is relatively more refracted (refraction in one direction, which reduces the elevation angle) when it hits the flank 4a meets.

Thus, the asymmetrical prism board makes a change in direction towards the forward direction, which is more effective than the change in direction which causes the symmetrical prism board at which the corresponding flanks 4b have substantially the same angle of inclination.

In other words, in order to improve the efficiency of the direction change, it is more advantageous for the inclination angle φa of the flank 4a , incident on the light, to be interpreted smaller than the inclination angle φb the flank 4b which is used for the direction change (φa <φb), as the flanks 4a and 4b to design with equal angles of inclination.

6 shows examples of preferred inclination angles φa and φb. The meanings and values of the reference symbols, which are given in 6 are assigned to each angle, are explained below.

φ2; Angle of the propagation direction of a beam B3, which represents light, that of the exit surface 5 is sent out. For example, φ2 is about 63 ° if the matrix of the light scattering guide plate 1 made of polymethylmethacrylate (PMMA with a refractive index of 1.492).

φa, φb; For example, inclination angle φa = 15 ° and φb = 32.5 ° measured against the reference direction (the thickness direction of the prism sheet) N, which satisfy the condition φ2 = about 63 °.

φ1; Inclination angle of the representative beam B3 on the flank 4a , φ1 is about 12 ° under the condition mentioned.

φ2; Angle below the representative beam B3 on the flank 4a is broken. Under the condition mentioned, φ2 = about 8 °.

φ3; Angle at which the representative beam B3 at the flank 4b is reflected (total reflection). Under the condition mentioned, φ3 = about 34 °.

φ4; Angle under which the representative beam B3 after the reflection (total reflection) at the flank 4b rises. Under the condition given, φ4 = approximately 91.5 ° ((90 ° - 32.5 °) + 34 °).

7 shows a view showing the behavior of light in the environment of the outer surface of the prism board 4 ' explained. It shows a portion of one of the prism element lines as viewed from the light source device. Representative rays, reflected in the prism board 4 ' propagate toward the forward direction, are denoted by the reference C1 and C2.

When the prism tip angle φ4 of the prism element lines on the outer surface is approximately 90 °, all or most of the light represented by the representative rays C1 and C2 will be internal to the edges 4c and subsequently 4d reflected (this is usually a total reflection) or on the flanks 4d and subsequently 4c , As a result, they are shifted laterally and become return beams D1 and D2 (beams that propagate in the reverse direction).

9 Fig. 12 is a view explaining the behavior of the return rays D1 and D2 in the vicinity of the inner surface. The majority of the return beams enter the light scattering guide plate 1 recycled. The in the light scattering guide plate 1 returned light is in the light scattering guide plate 1 subjected to a second scattering process and a reflection process on the rear surface 6 or the reflector 3 and then again from the exit surface 5 the light scattering guide plate 1 sent out, so it again on the prism board 4 ' meets.

In this process, the light goes through a variety of paths. Therefore, the propagation direction of the light has considerably expanded when it is returned to the prism board 4 ' meets. A considerable part of the light falls on the flanks at low angles 4c or 4d , see the illustration at C3 and C4, and is emitted from there in the form of the rays D3 and D4 in the forward direction.

By forming the outer surface of the prism board 4 ' As a prism surface it is thus possible to prevent light directly from the prism board 4 ' is sent out without following any return route.

In other words, rays from the same microscopic area of the outer surface of the prism board 4 ' are radiated through many different paths and thereby produce a uniform and soft illumination light. In particular, the generation of non-uniform illumination by reflection projection in areas close to the incident surface is prevented by suppressing the direct emission of strong components in the propagation direction.

7 and 9 are based on the assumption that the representative rays C1 and C2 propagate substantially in the forward direction and that the prism peak angle φ4 is approximately 90 °. However, a similar effect can be expected if the propagation direction of the representative beams C1 and C2 and the prism peak angles φ4 deviate to some extent from these conditions.

One practically realizable area for the prism tip angle φ4 is between 70 ° and 130 °. A smaller one Prism tip angle as 70 ° leads to a considerable Reduction of the convergence effect of the propagation direction of the light in the forward direction bundles in a plane in the transverse direction. This will cause the brightness the surface light source device lower.

If the prism tip angle φ4 is too large, a major portion of the representative rays C1 and C2 that move substantially in the forward direction will be directly from the flanks 4c and 4d radiated. As a result, one can expect no splitting of the pathways of the light, the prism board 4 ' emitted.

8th shows an example of such a situation for a case where φ4 = 160 °. A major part of the representative rays C1 and C2, see 8th that move substantially in the forward direction is from the flanks 4c and 4d emitted directly in the form of the radiated beams D1 and D2.

The reverse propagation (return) by total reflection occurs at an angle for an incident beam, denoted by reference C5. This contributes little to the splitting of the pathways of light that make up the prism board 4 ' emitted.

10 (a) and 10 (b) show curves with the measurement results of the angle characteristics of illumination light in the arrangement in FIG 4 under the conditions 6 , Both curves show the measurement results for symmetrical prism charts as well as for asymmetric prism charts under the same measuring conditions. Further shows 11 a curve of the angular properties of the arrangement with which the curves in 10 (a) and 10 (b) were won. However, the prism plates are removed to the effect of the prism board 4 ' highlight.

In each of these curves, the ordinate indicates the brightness of the luminous surfaces (the outer surfaces of the prism plates 4 and 4 ' ) measured in cd (candela) / m ² . The abscissa represents the direction in which the brightness is measured (the direction of the line of sight of the brightness meter). For 10 (a) and 11 An angular pass was made in the direction of line of sight of the brightness meter in a portion of the light scattering guide plate 1 in the longitudinal direction. For 10 (b) An angular pass was made in the direction of line of sight of the brightness meter in a portion of the light scattering guide plate 1 in the transverse direction.

In The angle 0 ° represents the two curves forward direction represents.

Like the curve in 11 shows, has the light scattering guide plate containing a matrix made of polymethyl methacrylate (PMMA with a refractive index of 1.492), a significant peak of the emitted light in a direction of approximately 63 ° in the longitudinal section.

In 10 (a) the curve G1 represents the result of the passage in the same longitudinal section for the arrangement from which the result in 11 but with an added asymmetric prism board (φa = 15 °, φb = 32.5 °). The curve G2 represents the result of the passage in the same longitudinal section for the arrangement from which the result in 11 but with an added symmetrical prism board (with a prism peak angle of 65 °).

Similarly, in 10 (b) the curve G3 represents the result of the passage in cross section for the arrangement from which the result in 11 but with an added asymmetric prism board (φa = 15 °, φb = 32.5 °). The curve G4 represents the result of the run in the same cross-section for the arrangement from which the result in 11 but with an added symmetrical prism board (with a prism peak angle of 65 °).

• (1) Sowohl in der Längsrichtung als auch der Querrichtung liefert die symmetrische oder die asymmetrische Prismentafel Beleuchtungslicht, das seinen Spitzenwert im Wesentlichen in Vorwärtsrichtung aufweist.
• (2) Aus dem Vergleich der Kurven G1 und G3 mit den Kurven G2 und G4 geht jedoch hervor, dass die asymmetrische Prismentafel einen Spitzenhelligkeitswert liefert, der 10 bis 20 Prozent größer ist als der Wert, den man mit der symmetrischen Prismentafel erreicht.
• (3) Die Kurve G2 der Kurven in 10(a) zeigt eine Verringerung der Helligkeit Q1 in einer Richtung, die relativ nahe an der Vorwärtsrichtung liegt (in der Nähe von –15°). Im Gegensatz dazu zeigt sie eine Zunahme der Helligkeit Q2 in einer Richtung, die relativ weit von der Vorwärtsrichtung entfernt ist (in der Nähe von –40°). Eine derartige unerwünschte Charakteristik ist in der Kurve G1 für die asymmetrische Prismentafel nahezu beseitigt, die nur eine geringe Spur Q3 zeigt.

From the measurement results you can see the following results.

• (1) In both the longitudinal direction and the transverse direction, the symmetrical or asymmetrical prism sheet provides illumination light having its peak substantially in the forward direction.
• (2) From the comparison of curves G1 and G3 with curves G2 and G4, however, it is apparent that the asymmetrical prism sheet provides a peak brightness value that is 10 to 20 percent greater than the value achieved with the symmetrical prism sheet.
• (3) The curve G2 of the curves in FIG 10 (a) shows a reduction in brightness Q1 in a direction relatively close to the forward direction (near -15 °). In contrast, it shows an increase in the brightness Q2 in a direction relatively far from the forward direction (near -40 °). Such an undesirable characteristic is almost eliminated in the asymmetrical prism board curve G1 which shows only a small trace Q3.

Out It is clear from the above information that the arrangement in which an asymmetrical prism board is used, considerable Improvements over having the arrangement in which uses a symmetrical prism board is, both in terms of brightness in the direction the peak value (essentially the forward direction) as well as the shape the brightness curve.

The invention can be adapted to surface light source devices or liquid crystal displays in various other arrangements. For example, various modifications are made in the shape of the light scattering guide plate 1 and the number and shape of the light source devices L possible. 12 to 15 show examples of such modifications in the form of sketched partial views. The arrangements, positions, functions, orientations, etc. of the asymmetrical prism sheet or other components are not described to avoid repetition.

12 shows an arrangement in which a light scattering guide plate 1 is used in the form of a flat plate and a light source device L along an end face of the plate is arranged (a first alternative embodiment). It differs from the embodiment in FIG 4 only through the cross sectional shape of the light scattering guide plate 1 ,

In the arrangement in 13 becomes a light scattering guide plate 1 used in the form of a flat plate and two light source devices L, which are arranged on the opposite end faces of the plate (a second alternative embodiment). It differs from the embodiment in FIG 4 by the cross-sectional shape of the light scattering guide plate 1 and the number of light source devices L used.

Another difference is that the orientation of the flanks on the inside surface of the prism board 4 ' along the center line FF has been reversed. Specifically, the flanks with a smaller inclination angle are formed to face the right light source device L on the right side of the center line FF, and the flanks with a smaller inclination angle are formed to be on the left side of the center line FF to the left light source device L show.

In the arrangement in 14 becomes a light scattering guide plate 1 used, which represents a combination of straight wedge-shaped structures, wherein the wedge-shaped parts abut each other (a third alternative embodiment). On each side of the plate, a light source device L is arranged. As in the case of 14 the orientation of the flanks is shown on the inner surface of the prism board 4 ' reversed along the center line FF. Specifically, the flanks with a smaller inclination angle are formed to face the right light source device L on the right side of the center line FF, and the flanks with a smaller inclination angle are formed to be on the left side of the center line FF to the left light source device L show.

In the arrangement in 15 is the back of the light scattering guide plate 1 arcuate design, and on each side of a light source device L is attached (a fourth alternative embodiment).

In this case, the orientation of the flanks on the inner surface of the prism board 4 ' again at the center line FF vice versa. Specifically, the flanks with a smaller inclination angle are formed to face the right light source device L on the right side of the center line FF, and the flanks with a smaller inclination angle are formed to be on the left side of the center line FF to the left light source device L show.

The in the described embodiments used prism charts are double orthogonal prism surfaces, at those prism surfaces with a plurality of prism element lines on both sides of the panel are formed. However, it is not essential that the outer surface of a such prism board is a prism surface.

A fundamental optical function required for the outer surface of a prism sheet is that it shifts a beam in a lateral direction and then translates the direction of the beam to the inner surface (to produce a return light component). Therefore, you can the prism element lines on the outer surface of the prism board 4 ' with double orthogonal prism surfaces used in the described embodiments, replace with lens element rows that provide similar effects as prism elements.

16 shows a view explaining a fifth alternative embodiment of the invention, in which such prism board is used with a prism surface and a lens field surface. As in 4 For better visibility in the drawing, the interval between the light scattering guide plate 1 and the lines of the prism elements and the distance and the depth of the lines of the prism elements exaggerated.

The fifth embodiment corresponds to an arrangement obtained when using the asymmetrical prism board 4 ' with two orthogonal prism faces having prism element rows on both sides thereof, in the embodiment in FIG 4 through a prism board 4 '' replaced with a prism surface and a lens field surface.

Near a light incident surface, the larger the thickness of a light scattering guide plate 1 is determined, which has a wedge-shaped cross section, a light source device (fluorescent lamp) L is arranged. The prism board 4 '' is aligned so that the lines of the lens elements formed on the outer surface of the panel are in a direction substantially perpendicular to the incident surface (light source device L).

The configuration and function of the other components next to the prism board 4 '' do not differ from the embodiment in 4 and are not described to avoid repetition. As in the arrangement in 4 For example, a liquid crystal display is constructed by placing a known liquid crystal display panel LP (not shown) outside the prism sheet 4 '' install.

In the light scattering guide plate 1 introduced light is guided to an end face, which determines the smaller thickness of the plate. At this time, the light in the light scattering guide plate becomes 1 scattered and on a reflector 3 reflected. During this process, illumination light will gradually move towards the prism panel 4 '' emitted.

The structure of the prism board 4 '' and the structure and function of the inner surface (asymmetric prism surface) are generally the same as the prism sheet 4 ' and are not described to avoid repetition.

In short, lines with asymmetric prism elements are as in 5 (b) or 6 repeating on the inside surface of the prism board 4 '' educated. As already mentioned, the effect of such prism element rows effectively produces light that is in the prism panel 4 '' moved in the forward direction.

As in the case of the prism board 4 ' reaches light, reflected in the prism board 4 '' moved in the forward direction, finally, the inner surface of the lens element rows, which on the outer surface of the prism board 4 '' are formed.

17 shows the general arrangement of the lens element rows, which on the outer surface of the prism board 4 '' are designed for the type with prism surfaces and lens field surfaces, and the behavior of light in the vicinity of the lens element line analogous to 7 , 17 shows a cross-section of one of the lens element rows as viewed from the light source device L. Representative rays that appear in the prism board 4 '' propagate in the forward direction are denoted by the reference numerals C1 and C2.

Of the representative Ray C1 represents light that moves in a plane, in the transverse direction to the forward direction lies. The representative Beam C2 represents light that is in a plane in the transverse direction moved, in a direction that is a small angle against the forward direction having.

The Lens element rows generally have a semi-cylindrical profile and contain a convexly curved surface in at least part of the elements. In this embodiment is a convex curved surface installed, which is near the top is smooth. All or most of the lens elements may be convex curved surfaces be formed. Furthermore, one can have a concave curved surface in the Accommodate valley between adjacent lens element rows.

One Main part of a representative Beam C1, which is close of such a tip portion is used as the illumination beam D1 in the forward direction radiated. In contrast, a considerable part or the main part a representative Beam C1, which strikes a region remote from the tip, dependent from the angle of incidence due to the internal reflection in the transverse direction shifted and subjected to a second internal reflection, so a return beam D1 is created.

Further becomes a main part of a representative Beam C2, which is close such a tip hits diagonally in a plane in the transverse direction emitted as the illumination beam D1. A considerable part or the main part a representative Beam C2, which hits an area remote from the tip, becomes dependent from the angle of incidence due to the internal reflection in the transverse direction although the light path is slightly off the path of the representative Beam C1 differs, and subjected to a second internal reflection, with it a return ray D1 is created.

The behavior of the return rays D1 and D2 near the inner surface is similar to the behavior in the prism sheet 4 ' , In particular, as based on 9 described a main part of the return beams in the light scattering guide plate 1 returned. The in the light scattering guide plate 1 returned light is in the light scattering guide plate 1 scattered again and on the back surface or the reflector 3 reflected. Then it gets back from the exit surface 5 the light scattering guide plate 1 blasted to make it back to the prism board 4 '' meets.

In this process, a plurality of light paths occur. Therefore, the propagation direction of the light has considerably expanded when it is returned to the prism board 4 '' meets. Thus, the distribution is the light expanded paths for the re-incident light in the transverse plane. This reinforces components in diagonal directions, which in 17 represented by the representative rays C2.

This provides a mechanism that the prism board 4 is similar to different light paths based on the generation of return beams. In other words, rays from the same microscopic area of the outer surface of the prism board 4 '' are radiated in the forward direction (in a plane in the longitudinal direction), through many different paths, thereby producing a uniform and soft illumination light.

Especially The generation of a non-uniform brightness by reflection projection in areas close to the incidence area prevented by the direct Transmission of strong components in the propagation direction is suppressed.

At the surface light source device in FIG 16 You can make various modifications, for example, arrangements with a double-orthogonal prism board. For example, in the alternative arrangements according to the described second to fourth embodiments (see 12 to 15 ) the prism board 4 ' with doubly orthogonal prism faces through a prism sheet with a lens array element prism face.

19 (a) and 19 (b) are curves showing the measurement results of the angle characteristics of illumination light in the arrangement in FIG 16 demonstrate. It became a light scattering guide plate 1 used with a standard size of 4 inches. The conditions for the inner surface (prism surface) of the prism board 4 '' agree with the conditions in 6 match. Furthermore, the conditions for the outer surface (lens field surface) of the prism sheet are correct 4 '' with the conditions in 18 match.

Especially is a tangential angle of 60 ° both edge portions of each lens element row set up, and it's a convex curved one area attached, which has a gradient which gradually decreases towards the tip.

In each of these curves, the ordinate indicates the brightness of the illuminating surface (the outer surface of the prism plates 4 '' ) measured in cd (candela) / m ² . The abscissa represents the direction in which the brightness is measured (the direction of the line of sight of the brightness meter). For 19 (a) An angular pass was made in the direction of line of sight of the brightness meter in a portion of the light scattering guide plate 1 in the longitudinal direction. For 19 (b) An angular pass was made in the direction of line of sight of the brightness meter in a portion of the light scattering guide plate 1 in the transverse direction.

In The angle 0 ° represents the two curves forward direction represents.

• (1) Sowohl in der Längsrichtung als auch in der Querrichtung wird ein Beleuchtungslicht erzeugt, das einen deutlichen Spitzenwert im Wesentlichen in der Vorwärtsrichtung hat.
• (2) Sowohl in der Längsrichtung als auch in der Querrichtung hat die Helligkeitskurve ein gut eingestelltes Profil mit einer geeigneten Breite und einer hohen Symmetrie.

From the measurement results you can see the following results.

• (1) In both the longitudinal direction and the transverse direction, an illumination light having a marked peak substantially in the forward direction is generated.
• (2) In both the longitudinal direction and the transverse direction, the brightness curve has a well-adjusted profile with a suitable width and a high symmetry.

From the above illustration, it appears that the prism board 4 '' with the lens field surface prism surface such as the asymmetrical prism sheets described, exhibits excellent characteristics in both the peak direction (substantially the forward direction) brightness and the shape of the brightness curve.

To the Finally, there is a supplementary Description of the materials for the prism sheet and the light scattering guide plate used in the invention and the description of a method of manufacturing these parts.

For the in of the invention used prism board and light scattering guide plate one can use different polymer materials as base (matrix). In Tables 1 and 2 are common Matrix materials shown.

you These materials can be unchanged because a prism sheet is usually a transparent one Component is. Should flat surfaces the prism board are processed like satin, so you can known Use blasting method. One can known plastic film molding process for forming a prism surface insert a desired one Prism tip angle, and a lens field surface, which has a desired shape Has. A light scattering guide plate, in which a polymer material serves as a basis, you can with the help manufacture the following manufacturing process.

One the method is to use a molding process which contains a step in the two or more types of polymers are mixed and ground. The two or more polymer material types in any shape (eg. Pellets) and with refractive indices which differ from one another, are mixed, heated and ground (mixing and milling step). The mixed and ground liquid material becomes high pressure in a metal mold of an injection molding machine injected. Subsequently it is cooled and solidified to give a sprayed product. The Shape of the metal mold is designed to provide a desired light scattering guide plate receives.

The two or more types of polymers with different refractive indices, the mixed and ground, mix before solidification not completely together. As a result, they solidify with non-uniform (fluctuating) local concentrations and provide a sprayed product with uniform Scattering power.

The Mixed and ground material can be put into a cylinder Inject injection molding machine and extrude in the usual way, so that you have a desired receives pressed product.

There are many possibilities for the combination and the mixing ratio of such a polymer mixture. It is preferred to focus on the refractive index of each material and the strength and properties of the structure with nonuniform refractive indices, which are determined by the shaping is generated (scattering and illumination parameters E, correlation distance a, root mean square τ of the fluctuation of the dielectric constant).

Common polymer materials, which can be used, are shown in Table 1 and 2.

According to one another method for producing materials comprising a light scattering guide plate form a material in the form of particles with a refractive index, which differs from the refractive index of the polymer material, evenly in the polymer material distributed (the difference in the refractive index is 0.001 or more).

To the procedures for a uniform distribution a material in particulate form is useful, the suspension polymerization belongs. In this process, a particulate material is added to a monomer. The material in particle form becomes a polymerization reaction by immersion in hot water set in motion so that the material evenly distributed in particle form becomes. This preserves a polymer material. This raw material can be molded to a light scattering guide plate with desired Make construction.

A Suspension polymerization can be done with various material combinations in the form of particles and monomers (combinations of particle concentrations, the particle size, the refractive indices etc.), so you get numerous types of material. These materials can you mix and shape specifically to light scattering guide plates produce, which have different characteristics. The particle concentration let yourself easily control by adding a polymer that does not Contains particulate material.

One another applicable method for the uniform one Distribution of a material in particle form consists in mixing and Milling a polymeric material and a material in particulate form. In this case, milling and forming (pelleting) can again with different material combinations in the form of particles and Monomers occur (combinations of particle concentrations, the Particle size, the Refractive indices etc.). These materials can be mixed specifically and shape to light scattering guide plates to produce with different properties.

moreover you can the polymer mixing process and the mixing process for a material in particle form as described combine. For example, can when mixing and grinding polymers with different Refractive indices mix a material in particle form. Because these manufacturing processes are known, the manufacturing conditions, etc. are no longer described in detail.

• (1) Man ordnet eine Oberflächen-Lichtquellenvorrichtung an, die gesehen in der Hauptbetrachtungsrichtung (im Wesentlichen der Vorwärtsrichtung) einen verbesserten Helligkeitspegel aufweist.
• (2) Man ordnet eine Oberflächen-Lichtquellenvorrichtung an, bei der der Helligkeitspegel mit zunehmender Winkelabweichung von der Hauptbetrachtungsrichtung (im Wesentlichen der Vorwärtsrichtung) allmählich abfällt, und in der die Ausgabe von Beleuchtungslicht in Betrachtungsrichtungen unterdrückt wird, in der eine Betrachtung weniger wahrscheinlich ist, um eine nutzlose Beleuchtung zu vermeiden.
• (3) Derartige Eigenschaftsverbesserungen erhöhen die Anwendbarkeit einer Oberflächen-Lichtquellenvorrichtung für die Hinterleuchtung einer Flüssigkristallanzeige.
• (4) Die Erfindung stellt eine neuartige asymmetrische Prismentafel bereit, die man für derartige Oberflächen-Lichtquellenvorrichtungen oder Flüssigkristallanzeigen einsetzen kann.

The features described in detail above can be summarized as follows.

• (1) Arranging a surface light source device having an improved brightness level as seen in the main observation direction (substantially the forward direction).
• (2) arranging a surface light source device in which the brightness level gradually decreases with increasing angular deviation from the main viewing direction (substantially the forward direction), and in which the output of illumination light in viewing directions in which viewing is less likely, to avoid useless lighting.
• (3) Such property improvements increase the applicability of a surface light source device for backlighting a liquid crystal display.
• (4) The invention provides a novel asymmetric prism sheet which can be used for such surface light source devices or liquid crystal displays.

Claims (9)

Prism board ( 4 ' . 4 '' ) for use in altering the directional propagation characteristics of light having an exit surface ( 5 ) a light scattering guide plate ( 1 ), which has an incident surface ( 2 ), which receives light, the prism sheet having a first surface on which rows of prism elements are aligned in a first direction, and a second surface, on which rows of refractive elements are aligned in a second direction, which is perpendicular to the first direction wherein the rows of refractive elements on the second surface are provided with surfaces (e.g. 4c . 4d ), which cause a beam in the prism board ( 4 ' . 4 '' ) is directed in a forward direction, is displaced in the first direction, and then thrown back to the first surface, characterized in that the rows of prism elements on the first surface alternate the repetitions of a slope ( 4a ) having a first relatively small inclination angle (φa) with respect to the thickness direction (N) of the prism board ( 4 ' . 4 '' ), and a slope ( 4b ) having a second relatively large inclination angle (φb) with respect to the thickness direction (N), and that the inclinations ( 4b ) having the second inclination angle (φb) toward the incident surface ( 2 ), whereas the inclinations ( 4a ) having the first inclination angle (φa) away from the incident surface ( 2 ) are directed. The prism sheet according to claim 1, wherein the refractive elements Are prism elements. The prism sheet according to claim 1 or 2, wherein the second relatively large Inclination angle (Φb) approximately 32.5 degrees. The prism sheet of claim 3, wherein the first relative small angles of inclination (Φa) approximately 15 degrees and the second relatively large one Inclination angle (Φb) approximately 32.5 degrees. Prism board according to claim 2 or claim 3 or 4 if dependent of claim 2, wherein the prism tip angle of the rows of prism elements on the second surface approximately 96 degrees. Prism board according to claim 2 or claim 3 or 4 if dependent of claim 2, wherein the prism tip angle of the rows of prism elements on the second surface in the range of 70 degrees to 130 degrees. Prism board according to claim 1 or claim 3 or 4 if not dependent of claim 2, wherein the refractive elements are lens elements. A surface light source device comprising a light scattering guide plate ( 1 ), a main light source device (L), which on one side of the light scattering guide plate ( 1 ) and light in an incident surface ( 2 ) of the light scattering guide plate ( 1 ), a prism board ( 4 ) along an exit surface ( 5 ) a light scattering guide plate ( 1 ), and a reflector ( 3 ) located on a surface opposite the exit surface ( 5 ), characterized in that the prism board ( 4 ' . 4 '' ) according to any preceding claim and arranged such that the first direction parallel to the incident surface ( 2 ) of the light scattering guide plate ( 1 ) and that the prism inclinations ( 4b ) having the second inclination angle (φb) toward the incident surface ( 2 ), whereas the prism inclinations ( 4a ) having the first inclination angle (φa) directed away from the incident surface. Liquid crystal display, which comprises: a liquid crystal panel; and a surface light source device, which serves the lighting from behind, characterized in that the surface light source device according to claim 8 is designed.